Search PubMed⌕ Search

Biomedical subjects

M Green

Publications and source records attributed to M Green.

At least 271 records · Page 15Linked to original sources
PubMed1995

Transcription factor TFIID is a direct functional target of the adenovirus E1A transcription-repression domain.

The 243-amino acid adenovirus E1A oncoprotein both positively and negatively modulates the expression of cellular genes involved in the regulation of cell growth. The E1A transcription repression function appears to be linked with its ability to induce cellular DNA synthesis, cell proliferation, and cell transformation, as well as to inhibit cell differentiation. The mechanism by which E1A represses the transcription of various promoters has proven enigmatic. Here we provide several lines of evidence that the "TATA-box" binding protein (TBP) component of transcription factor TFIID is a cellular target of the E1A repression function encoded within the E1A N-terminal 80 amino acids. (i) The E1A N-terminal 80 amino acids [E1A-(1-80)protein] efficiently represses basal transcription from TATA-containing core promoters in vitro. (ii) TBP reverses completely E1A repression in vitro. (iii) TBP restores transcriptional activity to E1A-(1-80) protein affinity-depleted nuclear extracts. (iv) The N-terminal repression domain of E1A interacts directly and specifically with TBP in vitro. These results may help explain how E1A represses a set of genes that lack common upstream promoter elements.

Adenovirus E1A Proteins↗
PubMed1995

Transcriptional repression by human adenovirus E1A N terminus/conserved domain 1 polypeptides in vivo and in vitro in the absence of protein synthesis.

The human adenovirus E1A 243R protein (243 residues) transcriptionally represses a set of cellular genes that regulate cellular growth and differentiation. We describe two lines of evidence that E1A repression does not require cellular protein synthesis but instead involves direct interaction with a cellular protein(s). First, E1A 243R protein represses an E1A-repressible promoter in the presence of inhibitors of protein synthesis, as shown by cell microinjection-in situ hybridization. Second, E1A 243R protein strongly represses transcription in vitro from promoters of the E1A-repressible genes, human collagenase, and rat insulin type II. Repression in vitro is promoter-specific, and an E1A polypeptide containing only the N-terminal 80 residues is sufficient for strong repression both in vivo and in vitro. By use of a series of E1A 1-80 deletion proteins, the E1A repression function was found to require two E1A sequence elements, one within the nonconserved E1A N terminus, and the second within a portion of conserved region 1 (40-80). These domains have been reported to possess binding sites for several cellular transcription regulators, including p300, Dr1, YY1, and the TBP subunit of TFIID. The in vitro transcription-repression system described here provides a powerful tool for the further analysis of molecular mechanism and the possible role of these cellular factors.

Adenovirus E1A Proteins↗
PubMed1995

Neurotoxicity of the human immunodeficiency virus type 1 tat transactivator to PC12 cells requires the Tat amino acid 49-58 basic domain.

The acquired immunodeficiency syndrome (AIDS) frequently involves the central nervous system (CNS) and manifests as dementia due to encephalitis or diffuse neurodegeneration. Human immunodeficiency virus type 1 (HIV-1) proteins, potentially transported into the CNS by mononuclear inflammatory cells, have been implicated in the etiology of this HIV-1 associated neurological dysfunction. Here we investigate the neurotoxicity of the essential HIV-1 regulator protein Tat in vivo after microinfusion into the rat brain and in vitro using PC12, NG108-15, and GT17 neuronal cell lines. Infusion of either chemically synthesized Tat (Tat86) or recombinant Tat (rTat) into the striatal gray matter in Sprague-Dawley rats resulted in postural deviation ipsilateral to the infusion, a clinical presentation in rats associated with complete striatal dysfunction. Histologic examination 3 days after infusion revealed massive necrosis in the area of the distribution of the infusion. Infusion of heat denatured rTat, peptide Tat49-58, or peptide Tat57-86 did not result in clinically or histologically detectable brain damage. After 3 days incubation in vitro, the lethal dose for half (LD50) of PC12 cells due to rTat was 5 micrograms/ml. The LD50 for Tat86 under the same conditions was 10 micrograms/ml. Tat49-58 and Tat57-86 peptides were not toxic in vitro even at 10-fold higher doses. At 5 micrograms/ml, rTat was toxic to 100% of GT17 cells after 24 hr. At 5 micrograms/ml, Tat86 was toxic to 90% of the NG108-15 cells after 7 days of treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Acquired Immunodeficiency Syndrome↗
PubMed1995

Serotonin depletion by 5,7-dihydroxytryptamine does not affect G protein subunit levels in rat cortex.

To investigate the role of G proteins in denervation supersensitivity of the CNS serotonergic system, we examined the effect of lesioning serotonergic neurons on the abundance of cerebral cortical membrane G protein subunits in rats. Three weeks after intracisternal injection of 5,7-dihydroxytryptamine (5,7-DHT), which significantly reduced cortical 5-hydroxytryptamine (5-HT; -90%) and 5-hydroxyindoleacetic acid (approximately 98%) levels, no statistically significant differences were observed for G alpha s-1, G alpha s-s, G alpha i1, G alpha i2, G alpha q/11, G alpha 0, G beta 1 and G beta 2 immunoreactivity levels between sham-lesioned and 5,7-DHT lesioned rats. These data suggest that the functional supersensitivity of 5-HT neuronal system often observed following lesions of 5-HT fibers may not involve changes at the level of G proteins but may instead encompass other downstream elements of the 5-HT receptor signaling cascade.

Animals↗
PubMed1995

Incidence and risk factors associated with the development of cytomegalovirus disease after intestinal transplantation.

From May 1990 to March 1993, 38 patients (21 adults and 17 children) received 40 allografts that included the small bowel (14 isolated small bowel, 21 small bowel and liver, and 5 multivisceral transplantations). Fifteen patients (39%) had 26 episodes of CMV disease: 7 with one episode, 6 with two, and 1 each with three and four. CMV enteritis accounted for 21 (81%) of the episodes, hepatitis and pneumonitis for 2 each, and a viral syndrome for 1. Cox's proportional hazards univariate and multivariate analyses showed that significant first-episode risk factors were: CMV seropositive donors for negative recipients (relative risk [RR], 3.86; P = 0.02), the average daily plasma trough level of tacrolimus (RR, 2.15; P = 0.04), and total amount of steroid boluses (RR, 2.90; P = 0.02). CMV disease recurrence factors were: CMV seronegative recipients (RR, 8.60; P = 0.02) and total amount of steroid bolus pulses (RR, 12.39; P = 0.004). Because long courses of ganciclovir prophylaxis could not prevent the development of CMV disease, avoidance of CMV seropositive grafts in seronegative recipients and new strategies to prevent heavy immunosuppression without the penalty of rejection will be necessary to ameliorate this problem in intestinal transplant recipients.

Adolescent↗
PubMed1995

Methylfolate modulates potassium evoked neuro-secretion: evidence for a role at the pteridine cofactor level of tyrosine 3-hydroxylase.

We have previously shown that 5-methyltetrahydrofolate influences neuro-secretion. The present study more precisely characterises the processes involved and considers one probable site of action. Focusing on the tyrosine-noradrenalin axis in cerebellum we showed 5-methyltetrahydrofolate causes a significant reduction in the apparent K+ evoked secretion of noradrenalin to only 12.9% of control release. Evidence supports the idea that this could actually be due to increased synthesis leading to; depletion of reserves, possibly through leakage, exocytotic inhibition via activation of presynaptic receptors or end product inhibition by noradrenalin at the pteridine cofactor level of tyrosine hydroxylase: a) concomitant decreased measurement of perfusate and intracellular tyrosine with released noradrenalin following 5-methyltetrahydrofolate treatment supports the idea of increased transmitter turn over; b) kinetic studies indicate that at saturating concentrations of tyrosine and in the presence of an inhibitor of L-DOPA decarboxylase, 5-methyltetrahydrofolate partially duplicates the rate limiting behaviour of a synthetic pteridine cofactor--DL,2-amino-4-hydroxy-6,7,dimethyltetrahydropteridine. We debate whether, in vivo, CSF 5-methyltetrahydrofolate might interact at the tetrahydrobiopterin cofactor level of tyrosine hydroxylase and other aromatic amino-acid hydroxylases.

Animals↗
PubMed1995

Folding and assembly of a human MHC class II molecule in a cell-free system.

The assembly of a human major histocompatibility complex (MHC) class II molecule was investigated in a cell-free system capable of the synthesis, sequestration, and processing of the protein chains. As assessed by the conformation-sensitive monoclonal antibody L243, the formation of HLA-DR alpha/beta heterodimer required cotranslation of alpha and beta mRNA in the presence of both oxidized glutathione and canine pancreas endoplasmic reticulum (ER) vesicles. The assembly of alpha/beta dimer could also be initiated by the post-translational addition of oxidized glutathione. Using the post-translational assay system, we investigated the effect of the depletion of ER lumenal content proteins on the folding and assembly of the MHC class II chains. Both the rate and extent of folding of alpha chain and beta chain and the post-translational assembly of alpha/beta dimer is greatly reduced in the depleted ER vesicles. Conversely, the extent of aggregate formation is increased. Upon reconstitution of the depleted ER vesicles with lumenal proteins, the folding of alpha chain is accelerated and the assembly of alpha/beta dimer is increased.

Animals↗
PubMed1995

Parainfluenza and influenza virus infections in pediatric organ transplant recipients.

We retrospectively reviewed parainfluenza and influenza virus infections that occurred in pediatric organ transplant recipients at our hospital from January 1985 through September of 1992. Cultures of respiratory specimens revealed 45 infections in 42 transplant recipients (32 cases of parainfluenza and 13 cases of influenza virus infection). The following organs were transplanted: liver (28 patients), small bowel with and without liver (4), heart (3), lung with and without heart (5), and kidney (2). Clinical presentations of the patients and outcomes were similar regardless of the type of virus isolated or the type of organ transplanted. There were 20 cases in which patients had upper respiratory symptoms but did not require supplemental oxygen, nine cases in which patients required oxygen supplementation only, and eight cases in which the patients survived with mechanical ventilation. Eight patients died (five had parainfluenza, three had influenza virus infection); four children had serious concurrent infections (cytomegaloviral pneumonia in one patient, bacteremia in two, bacteremia and pneumonia in one). Factors associated with poor outcome for the entire group were age (increased morbidity and mortality if < 6 months old), augmentation of immunosuppression, and onset of infection within 1 month of transplantation. In this patient population, parainfluenza and influenza infections were important causes of morbidity and mortality.

Adolescent↗
PubMed1995

Bacteremia due to vancomycin-dependent Enterococcus faecium.

A recipient of small-bowel and liver transplants developed recurrent fever and polymicrobial bacteremia due to multiply resistant Enterobacter cloacae and an inducible VanB strain of Enterococcus faecium while receiving therapy with amikacin, imipenem, and vancomycin. These organisms could not be subcultured onto blood agar but did grow around the vancomyin disk on a direct-susceptibility test plate. Additional testing confirmed the strain as E. faecium, which would not grow in the absence of vancomycin. Growth around a disk containing D-alanyl-D-alanine was demonstrated. Spontaneous vancomycin-independent revertants were obtained at a frequency of approximately 1 x 10(-6). Two classes of vancomycin-independent revertants were obtained: one that was constitutively vancomycin resistant and one that was nonconstitutively vancomycin resistant. We hypothesize that the normal D-ala ligase is not expressed in the vancomycin-dependent strain; thus survival of these strains is dependent on expression of the VanB ligase, which produces a depsipeptide precursor that is resistant to vancomycin binding. This is the second reported case involving a clinically important vancomycin-dependent enterococcal strain. Awareness of the existence of these strains is important, especially when clinical and microbiological data are consistent with infection due to a fastidious or nutritionally-deficient organism.

Bacteremia↗
PubMed1995

A phase II trial of zeniplatin in metastatic melanoma.

A third-generation platinum analogue, zeniplatin, was administered at a dose of 145 mg/m2 intravenously over 60-90 minutes every 21 days as the initial chemotherapy to 21 patients with metastatic melanoma. Prehydration and mannitol diuresis was introduced after the first 7 patients. There were 17 males and 4 females. The median age was 52 (range: 29-81). ECOG performance status was 0 in 10 patients, 1 in 8 patients and 2 in 3 patients. Major disease sites were lymph nodes, skin, lung, liver, and bone. Patients received a median of 2 cycles (range: 1-7). Two patients achieved partial responses. One with nodal disease progressed after 166 days and the other with buccal mucosal disease after 142 days. A third patient showed partial regression of nodal disease but developed cerebral metastases. Gastrointestinal toxicity included WHO grade 3 vomiting in 8 patients and nausea in 2. Antiemetics were used, but ondansetron was not available. WHO grade 3 hematologic toxicities included neutropenia in 8 patients and anemia and thrombocytopenia in 1 patient. Thrombocytosis was seen in 35% of courses. Dosage reduction was required in 15% of courses and escalation in 5% of courses. Three patients developed phlebitis related to the infusion. One patient developed a reversible rise in serum creatinine, but, unlike other studies, no severe nephrotoxicity was reported. Zeniplatin demonstrated only modest activity in melanoma with significant gastrointestinal and hematologic toxicity.

Adult↗
PubMed1995

A phase II study of recombinant interferon-gamma following combination chemotherapy for patients with extensive small cell lung cancer. CALGB.

A total of 71 patients with extensive small cell lung cancer were enrolled in CALGB study 8733. Chemotherapy was administered with cisplatin 33 mg/m2, i.v. infusion days 1-3, doxorubicin 45 mg/m2 i.v. day 1, cyclophosphamide 800 mg/m2 i.v. day 1, and etoposide 80 mg/m2 i.v. infusion days 1-3 (PACE). Following four courses of PACE, patients achieving a CR or PR were started on recombinant interferon-gamma (rINF-gamma) 0.2 mg s.c. daily until grade IV toxicities or progression occurred. Of the 71 patients enrolled, 67 are evaluated (47 males and 20 females), median age 59 years, and median PS1. The response rate to PACE was 48/67, 72%. Grade 3-4 toxicities included granulocytopenia, thrombocytopenia, and five treatment-related deaths (7%). Forty-one patients were started on rINF-gamma. Of these 41 patients, 11 were in CR, 30 in PR. The objective response rate to rINF-gamma was 2/30 or 6.7%. Recombinant rINF-gamma is inactive in small cell lung cancer, even when the tumor burden has been substantially reduced by prior chemotherapy.

Antineoplastic Combined Chemotherapy Protocols↗